US4249108A - LaMg Aluminate phosphors activated by europium and lamps incorporating same - Google Patents

LaMg Aluminate phosphors activated by europium and lamps incorporating same Download PDF

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US4249108A
US4249108A US06/099,064 US9906479A US4249108A US 4249108 A US4249108 A US 4249108A US 9906479 A US9906479 A US 9906479A US 4249108 A US4249108 A US 4249108A
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Robert W. Wolfe
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Osram Sylvania Inc
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GTE Products Corp
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    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09KMATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7783Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals one of which being europium
    • C09K11/7792Aluminates

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  • This invention relates to aluminate phosphors, and more particularly relates to blue-emitting LaMg aluminate phosphors activated by europium, and to fluorescent lamps incorporating them.
  • Beta-alumina-type hexagonal magnetoplumbite structure was discovered in the La 2 O 3 -Al 2 O 3 binary system for the compound LaAl 11 O 18 , and the compound was found to have a solid solution region for ratios of La 2 O 3 to Al 2 O 3 from about 1:10 to 1:12.
  • R. S. Roth and S. Hasko J. American Ceramic Society, Vol. 41, (1958), p. 146. Fluorescence of La 2 O 3 .11Al 2 O 3 activated by Eu and Mn was published by M. Tamatani in 1974. (Japanese Journ. of App. Phys., Vol. 13, No. 6, June, 1974, p. 950-956).
  • Verstegen et al. disclose luminescent ternary aluminates and gallates exhibiting a hexagonal crystal structure.
  • the host compound LaMgAl 11 O 19 is disclosed as having the hexagonal or magneto plumbite structure and as falling within area "YSM" of the ternary diagram of FIG. 1 of the patent.
  • Example No. 85 of the patent sets forth the composition
  • compositions within the La 2 O 3 -MgO-Al 2 O 3 system although lying within a region of the composition diagram remote from the single phase magneto plumbite LaMgAl 11 O 19 and LaAl 11 O 18 compositions, nevertheless exhibit optimum brightnesses upon ultraviolet excitation.
  • the compositions of the invention are comprised of at least two of the phases; magneto plumbite, alpha-alumina and spinel, and fall within the diamond shaped area DEFG of the ternary diagram for La 2 O 3 -MgO-Al 2 O 3 of FIG. 1.
  • the blue-emitting phosphor compositions of the invention are useful either alone or in combination with one or more other phosphors in fluorescent lamps.
  • FIG. 1 is a portion of the ternary diagram for La 2 O 3 -MgO-Al 2 O 3 , showing regions for prior art compositions and compositions of the invention having superior brightnesses upon ultraviolet excitation;
  • FIG. 2 is a graph of relative intensity (arbitrary units) of luminescent emission versus wavelength of emission in nanometers for a composition of the invention.
  • FIG. 3 is a plan view of a fluorescent lamp, partly cut away, showing a fluorescent layer incorporating a luminescent phosphor composition of the invention.
  • region ABC labeled "Prior Art”
  • region DEFG encompassing the multiphase Eu-activated host compositions of this invention, exhibiting improved brightness of UV-excited luminescent emission. Region DEFG may also be described by the formula
  • the amount of Eu activator is not critical and may range from 2 to 20 mole %, or 0.02 to 0.20 moles per mole of host, but is preferably kept within the range 0.025 to 0.125 moles per mole of host.
  • FIG. 2 is a portion of the emission spectrum of a composition of the invention (composition No. 2 of the Example), showing the emission peak.
  • FIG. 3 is a plan view of a fluorescent lamp 10 of a conventional type, including glass envelope 11, end caps 12 and 14, with protruding connector pins 13a and b and 15a and b, a luminescent layer 16 coating the inside surface of the envelope 11.
  • a fill gas comprising Ar and Hg atoms is present inside envelope 11.
  • the layer 16 incorporates a Eu-activated luminescent composition from area DEFG of FIG. 1.
  • compositions of the invention may be prepared readily by blending the required amounts of appropriate starting materials and firing in a reducing atmosphere at an elevated temperature for a modest time interval.
  • Time, temperature and reducing atmosphere are not critical, but a mixture of nitrogen and hydrogen or hydrogen are preferred, a temperature range from 1500° C. to 1650° C. is preferred, and a time of from 1 to 5 hours is preferred.
  • the particular starting materials are not critical. Preferred are Al(OH) 3 ,MgO, La 2 O 3 and Eu 2 O 3 .
  • Example I Using the procedure of Example I, several phosphor samples were prepared having the compositions shown in Table I and FIG. 1. Phase assemblages obtained by x-ray diffraction analysis, along with relative brightnesses obtained by plaque measurements of phosphor powder excited with 254 nm radiation are also shown in the Table.
  • the phosphor was incorporated into a standard commercial-type 40 watt fluorescent lamp. After 100 hours of lamp operation, the lamp showed 99.1% maintenance, where maintenance is defined by: ##EQU1##
  • compositions 1, 2 and 3 of the invention exhibit relative brightnesses of 97, 100 and 98 percent, respectively, while prior art composition 4 exhibits only 95 percent relative brightness. It is also seen that compositions 1, 2 and 3 all contain the phases magneto plumbite and alpha alumina, and composition 3 additionally contains spinel. In contrast, the prior art composition 4 is entirely magneto plumbite.
  • a blue emitting LaMg aluminate phosphor activated by Eu and having a multiphase structure exhibits improved brightness over prior art single phase compositions, and also exhibits high maintenance, making such phosphor useful either alone or in combination with other phosphors in fluorescent lamps.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Luminescent Compositions (AREA)

Abstract

A blue emitting La Mg aluminate phosphor activated by Eu and having a multiphase structure, exhibits improved brightness over prior art single phase compositions, and also exhibits high maintenance, making such phosphor useful either alone or in combination with other phosphors in fluorescent lamps.

Description

BACKGROUND
This invention relates to aluminate phosphors, and more particularly relates to blue-emitting LaMg aluminate phosphors activated by europium, and to fluorescent lamps incorporating them.
The Beta-alumina-type hexagonal magnetoplumbite structure was discovered in the La2 O3 -Al2 O3 binary system for the compound LaAl11 O18, and the compound was found to have a solid solution region for ratios of La2 O3 to Al2 O3 from about 1:10 to 1:12. R. S. Roth and S. Hasko, J. American Ceramic Society, Vol. 41, (1958), p. 146. Fluorescence of La2 O3.11Al2 O3 activated by Eu and Mn was published by M. Tamatani in 1974. (Japanese Journ. of App. Phys., Vol. 13, No. 6, June, 1974, p. 950-956).
In U.S. patent application Ser. No. 509,438, assigned to the present assignee, R. W. Wolfe discloses luminescent mixed alkaline earth cation aluminates activated by Eu alone or with Mn, for example, Ba Mg aluminate activated by Eu.
In Netherlands Pat. No. 7,214,862, Verstegen et al. disclose luminescent ternary aluminates and gallates exhibiting a hexagonal crystal structure. The host compound LaMgAl11 O19 is disclosed as having the hexagonal or magneto plumbite structure and as falling within area "YSM" of the ternary diagram of FIG. 1 of the patent. Example No. 85 of the patent sets forth the composition
La.sub.0.93 Eu.sub.0.05 MgMn.sub.0.02 Al.sub.11 O.sub.19
having intensity maxima of luminescence at 452 and 515 nanometers.
SUMMARY OF THE INVENTION
In accordance with the invention, it has been discovered that certain blue-emitting Eu-activated phosphor compositions within the La2 O3 -MgO-Al2 O3 system, although lying within a region of the composition diagram remote from the single phase magneto plumbite LaMgAl11 O19 and LaAl11 O18 compositions, nevertheless exhibit optimum brightnesses upon ultraviolet excitation. The compositions of the invention are comprised of at least two of the phases; magneto plumbite, alpha-alumina and spinel, and fall within the diamond shaped area DEFG of the ternary diagram for La2 O3 -MgO-Al2 O3 of FIG. 1.
The blue-emitting phosphor compositions of the invention are useful either alone or in combination with one or more other phosphors in fluorescent lamps.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a portion of the ternary diagram for La2 O3 -MgO-Al2 O3, showing regions for prior art compositions and compositions of the invention having superior brightnesses upon ultraviolet excitation;
FIG. 2 is a graph of relative intensity (arbitrary units) of luminescent emission versus wavelength of emission in nanometers for a composition of the invention; and
FIG. 3 is a plan view of a fluorescent lamp, partly cut away, showing a fluorescent layer incorporating a luminescent phosphor composition of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, which is a portion of a ternary diagram for the La2 O3 -MgO-Al2 O3 system, there is shown region ABC, labeled "Prior Art", corresponding to region YSM of FIG. 1 of the Verstegen patent discussed above and encompassing Eu-activated host compositions having a single phase hexagonal magnetoplumbite crystal structure. Also shown is region DEFG, encompassing the multiphase Eu-activated host compositions of this invention, exhibiting improved brightness of UV-excited luminescent emission. Region DEFG may also be described by the formula
La.sub.x Mg.sub.y Al.sub.11 O.sub.16.5+y+(3 x/2)
where
x=0.351 to 0.750 and
y=0.351 to 0.750
The amount of Eu activator is not critical and may range from 2 to 20 mole %, or 0.02 to 0.20 moles per mole of host, but is preferably kept within the range 0.025 to 0.125 moles per mole of host.
When activated with divalent Eu, the host compositions become brilliant blue phosphors, which upon UV excitation exhibit luminescent emissions peaking in intensity at about 445±5 nanometers with a peak intensity halfwidth of about 75±5 nanometers. FIG. 2 is a portion of the emission spectrum of a composition of the invention (composition No. 2 of the Example), showing the emission peak.
FIG. 3 is a plan view of a fluorescent lamp 10 of a conventional type, including glass envelope 11, end caps 12 and 14, with protruding connector pins 13a and b and 15a and b, a luminescent layer 16 coating the inside surface of the envelope 11. A fill gas comprising Ar and Hg atoms is present inside envelope 11. The layer 16 incorporates a Eu-activated luminescent composition from area DEFG of FIG. 1.
The compositions of the invention may be prepared readily by blending the required amounts of appropriate starting materials and firing in a reducing atmosphere at an elevated temperature for a modest time interval. Time, temperature and reducing atmosphere are not critical, but a mixture of nitrogen and hydrogen or hydrogen are preferred, a temperature range from 1500° C. to 1650° C. is preferred, and a time of from 1 to 5 hours is preferred. The particular starting materials are not critical. Preferred are Al(OH)3,MgO, La2 O3 and Eu2 O3.
EXAMPLE I
A mixture of starting materials of
1.531 grams La2 O3
0.378 grams MgO
13.200 grams Al(OH)3
0.135 grams Eu2 O3
was fired at 1550° C. for four hours in a reducing atmosphere of 75 vol. % H2, 25 vol. % N2. The resulting phosphor had the approximate molar formulation:
La.sub.0.611 Mg.sub.0.611 Al.sub.11 O.sub.18.1 :0.05 Eu
and comprised about 80 percent magneto plumbite phase, 20 percent alpha alumina phase, and under UV excitation luminesced bright blue. A portion of the emission spectrum is shown in FIG. 2.
EXAMPLE II
Using the procedure of Example I, several phosphor samples were prepared having the compositions shown in Table I and FIG. 1. Phase assemblages obtained by x-ray diffraction analysis, along with relative brightnesses obtained by plaque measurements of phosphor powder excited with 254 nm radiation are also shown in the Table.
EXAMPLE III
Using the procedure of Example I, a phosphor composition was prepared having the approximate molar formulation:
La.sub.0.750 Mg.sub.0.750 Al.sub.11 O.sub.18.4
The phosphor was incorporated into a standard commercial-type 40 watt fluorescent lamp. After 100 hours of lamp operation, the lamp showed 99.1% maintenance, where maintenance is defined by: ##EQU1##
                                  TABLE I                                 
__________________________________________________________________________
Composition, Relative Brightness, and Phase Assemblages                   
For Points Shown in FIG. 1                                                
                                Phase                                     
No. In                                                                    
     Composition                                                          
           (Mol %)        Relative                                        
                                Assemblage                                
FIG. 1                                                                    
    1/2La.sub.2 O.sub.3                                                   
        MgO                                                               
           1/2A1.sub.2 O.sub.3                                            
               Host Molar Formula                                         
                          Brightness                                      
                                (percent)*                                
__________________________________________________________________________
1   3.75                                                                  
        3.75                                                              
           92.5                                                           
               La.sub..445 Mg.sub..445 Al.sub.11 O.sub.17.6               
                          97    65A, 35 a                                 
2   5   5  90  La.sub..611 Mg.sub..611 Al.sub.11 O.sub.18.0               
                          100   80A, 20 a                                 
3   6.0 6.0                                                               
           88.0                                                           
               La.sub..750 Mg.sub..750 Al.sub.11 O.sub.18.5               
                          98    85A, 5 a, 10S                             
4   7.69                                                                  
        7.69                                                              
           85  LaMgAl.sub.11 O.sub.19                                     
                          95    100A                                      
__________________________________________________________________________
 *Phases detected by xray diffraction. Relative amounts based on relative 
 peak heights and are approximate.                                        
 a = alpha alumina,                                                       
 A = magneto plumbite,                                                    
 S = spinel.                                                              
It may be seen from Table I and FIG. 1 that compositions 1, 2 and 3 of the invention exhibit relative brightnesses of 97, 100 and 98 percent, respectively, while prior art composition 4 exhibits only 95 percent relative brightness. It is also seen that compositions 1, 2 and 3 all contain the phases magneto plumbite and alpha alumina, and composition 3 additionally contains spinel. In contrast, the prior art composition 4 is entirely magneto plumbite.
While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.
INDUSTRIAL APPLICABILITY
A blue emitting LaMg aluminate phosphor activated by Eu and having a multiphase structure, exhibits improved brightness over prior art single phase compositions, and also exhibits high maintenance, making such phosphor useful either alone or in combination with other phosphors in fluorescent lamps.

Claims (4)

I claim:
1. A blue-emitting divalent europium activated lanthanum magnesium aluminate luminescent phosphor composition exhibiting a multiphase structure of either magneto plumbite and alpha alumina phases or magneto plumbite, alpha alumina and spinel phases and having the molar formula of
La.sub.x Mg.sub.y Al.sub.11 O.sub.16.5+y+( 3x/2)
where x lies between 0.351 and 0.750 and y lies between 0.351 and 0.750; said phosphor composition exhibiting a greater brightness than the corresponding divalent europium activated lanthanum magnesium aluminate luminescent phosphor composition having the molar formula LaMgA11 O19.
2. The composition of claim 1 wherein the europium activator is present in the amount of about 0.02 to 0.20 moles per mole of host.
3. The composition of claim 2 wherein the europium activator is present in the amount of from 0.025 to about 0.125 moles per mole of host.
4. A fluorescent lamp including the luminescent phosphor composition of claim 1.
US06/099,064 1979-11-30 1979-11-30 LaMg Aluminate phosphors activated by europium and lamps incorporating same Expired - Lifetime US4249108A (en)

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Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4606846A (en) * 1980-07-08 1986-08-19 Centre National De La Rechereche Scientifique Mixed rare earth metal, divalent transition metal, aluminum oxide
US4915869A (en) * 1985-10-21 1990-04-10 Commissariat A L'energie Atomique Mixed lanthanum-magnesium aluminates
US5105121A (en) * 1989-02-16 1992-04-14 Gte Laboratories Incorporated Lanthanum cerium aluminate phosphor and an electrical discharge device containing the same
US5143438A (en) * 1990-10-15 1992-09-01 Thorn Emi Plc Light sources
US5985174A (en) * 1997-09-22 1999-11-16 Samsung Display Devices Fluorescent material used in an active dynamic liquid crystal display device and method for manufacturing the same
US6117362A (en) * 1997-11-07 2000-09-12 University Of Georgia Research Foundation, Inc. Long-persistence blue phosphors
US20030059531A1 (en) * 2001-09-26 2003-03-27 Osram Sylvania Inc. Protective spinel coating for aluminate phosphors
US6660186B2 (en) 2001-10-31 2003-12-09 Matsushita Electric Industrial Co., Ltd. Method of making blue emitting aluminate phosphor for VUV excited light emitting device
US20040099844A1 (en) * 2002-11-21 2004-05-27 Matsushita Electric Industrial Co., Ltd. Stable blue phosphor for plasma display panel applications
US20040164277A1 (en) * 2003-02-25 2004-08-26 Yen William M. Long persistent phosphors and persistent energy transfer technique
US20060027786A1 (en) * 2004-08-04 2006-02-09 Intematix Corporation Aluminate-based blue phosphors
US20060158090A1 (en) * 2005-01-14 2006-07-20 Intematix Corporation Novel aluminate-based green phosphors
JP2008532896A (en) * 2005-03-11 2008-08-21 フォルシュングスツェントルム・ユーリッヒ・ゲゼルシャフト・ミット・ベシュレンクテル・ハフツング Insulating material and its manufacturing method and application
JP2008222989A (en) * 2007-03-16 2008-09-25 Nagoya Institute Of Technology Phosphor mixture and method for producing the same
EP1888709A4 (en) * 2005-03-30 2010-12-08 Daejoo Electronic Mat Co Ltd Lamp having good maintenance behavior of brightness and color coordinations
WO2011041657A1 (en) * 2009-10-01 2011-04-07 Cabot Corporation Particulate compositions having plural responses to excitation radiation
CN116837461A (en) * 2023-07-05 2023-10-03 国瑞科创稀土功能材料(赣州)有限公司 A divalent europium ion-activated aluminate scintillation crystal and its preparation method

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL7214862A (en) 1972-11-03 1974-05-07
US4161457A (en) * 1977-03-15 1979-07-17 Dai Nippon Toryo Co., Ltd. Process for preparing a divalent europium activated alkaline earth metal aluminate phosphor

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL7214862A (en) 1972-11-03 1974-05-07
US4161457A (en) * 1977-03-15 1979-07-17 Dai Nippon Toryo Co., Ltd. Process for preparing a divalent europium activated alkaline earth metal aluminate phosphor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Stevels et al., "J. Electrochem Soc.", vol. 123, No. 5, 1976, pp. 691-697. *

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4606846A (en) * 1980-07-08 1986-08-19 Centre National De La Rechereche Scientifique Mixed rare earth metal, divalent transition metal, aluminum oxide
US4915869A (en) * 1985-10-21 1990-04-10 Commissariat A L'energie Atomique Mixed lanthanum-magnesium aluminates
US5105121A (en) * 1989-02-16 1992-04-14 Gte Laboratories Incorporated Lanthanum cerium aluminate phosphor and an electrical discharge device containing the same
US5143438A (en) * 1990-10-15 1992-09-01 Thorn Emi Plc Light sources
US5985174A (en) * 1997-09-22 1999-11-16 Samsung Display Devices Fluorescent material used in an active dynamic liquid crystal display device and method for manufacturing the same
US6117362A (en) * 1997-11-07 2000-09-12 University Of Georgia Research Foundation, Inc. Long-persistence blue phosphors
US20030059531A1 (en) * 2001-09-26 2003-03-27 Osram Sylvania Inc. Protective spinel coating for aluminate phosphors
US6761971B2 (en) * 2001-09-26 2004-07-13 Osram Sylvania Inc. Protective spinel coating for aluminate phosphors
US6660186B2 (en) 2001-10-31 2003-12-09 Matsushita Electric Industrial Co., Ltd. Method of making blue emitting aluminate phosphor for VUV excited light emitting device
US6830706B2 (en) 2002-11-21 2004-12-14 Matsushita Electric Industrial Co., Ltd. Stable blue phosphor for plasma display panel applications
US20040099844A1 (en) * 2002-11-21 2004-05-27 Matsushita Electric Industrial Co., Ltd. Stable blue phosphor for plasma display panel applications
US20040164277A1 (en) * 2003-02-25 2004-08-26 Yen William M. Long persistent phosphors and persistent energy transfer technique
US6953536B2 (en) 2003-02-25 2005-10-11 University Of Georgia Research Foundation, Inc. Long persistent phosphors and persistent energy transfer technique
US20060027786A1 (en) * 2004-08-04 2006-02-09 Intematix Corporation Aluminate-based blue phosphors
US7390437B2 (en) 2004-08-04 2008-06-24 Intematix Corporation Aluminate-based blue phosphors
US20060158090A1 (en) * 2005-01-14 2006-07-20 Intematix Corporation Novel aluminate-based green phosphors
JP2008532896A (en) * 2005-03-11 2008-08-21 フォルシュングスツェントルム・ユーリッヒ・ゲゼルシャフト・ミット・ベシュレンクテル・ハフツング Insulating material and its manufacturing method and application
EP1888709A4 (en) * 2005-03-30 2010-12-08 Daejoo Electronic Mat Co Ltd Lamp having good maintenance behavior of brightness and color coordinations
JP2008222989A (en) * 2007-03-16 2008-09-25 Nagoya Institute Of Technology Phosphor mixture and method for producing the same
WO2011041657A1 (en) * 2009-10-01 2011-04-07 Cabot Corporation Particulate compositions having plural responses to excitation radiation
US8791439B2 (en) 2009-10-01 2014-07-29 Cabot Security Materials, Inc. Particulate compositions having plural responses to excitation radiation
CN116837461A (en) * 2023-07-05 2023-10-03 国瑞科创稀土功能材料(赣州)有限公司 A divalent europium ion-activated aluminate scintillation crystal and its preparation method
CN116837461B (en) * 2023-07-05 2024-02-06 国瑞科创稀土功能材料(赣州)有限公司 A divalent europium ion-activated aluminate scintillation crystal and its preparation method

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